Both sides do it. I see it on the right, too. It's just a different set of isms. Liberals want to live in a magic rainbow utopia that's impossible to achieve and conservatives want to live in a long bygone era that wasn't great in the first place. That's the oversimplification of it.
I try to keep an even keel. I'll admit I'm center-left. (I'm not a jobless, gay, transgender, hipster sipping PBR in a scarf.) Personally, I think today's left is too soft with its faux outrage over every little thing - from gender identity to body shaming to the race of people in ads, etc., but GD, today's right is pretty weak too with people who love to call others "snowflakes" crying over what ESPN talking heads say and, now, what athletes do before games. I don't care if you sit, stand, kneel, dance or strike the Karate Kid pose during the anthem, Bill. You know why? Because it's your right and if you're not violating my rights why would I care enough to even act offended, much less get offended.
"That’s fine, it’s healthy to disagree, but it’s not healthy to try to undermine an elected President from the word go."
In fairness, the right did the same thing with Obama eight years ago. Sen. Mitch McConnell himself said the GOP's lone legislative goal was to make Obama "a one-term president." The left did if during GWB's second term. They're doing it now for Trump. Don't act like this is brand new in 2017.
Blind partisanship, either way, is dangerous and creates sheep on both sides who refuse to listen to what the other side is saying simply because it's the other side. As long as the big two parties groom us to view the other half of the country as enemies, nothing will change. (Hint, they're both trying to dick us over to coddle the people who pay for their campaigns.)